Be aware that the nominal size on the sidewall and the actual size of a tire can vary rather a lot from brand to brand and model to model. I've had tires marked 700-32 and 700-28 that both measured 26 mm as installed on standard road rims and their roll-out for cyclometer calibration were both consistant with a true 26 mm. So the fact that one model "700-28" tire fits your frame and fork doesn't mean a different model will.